Recently, secondary batteries have been widely used in a medium and/or large-scale device such as a vehicle and a power storage device, as well as a small device such as a portable electronic device. In particular, since carbon-based energy is gradually depleted and concern about environment has been increasing, hybrid cars and electric vehicles are being highlighted worldwide including USA, Europe, Japan, and Korea.
In hybrid cars or electric vehicles, the most important component is a secondary battery pack providing a motor of a vehicle with a driving power. Since a driving power of a hybrid car or an electric vehicle is obtained through charging/discharging of a secondary battery pack, the hybrid car or the electric vehicle has various advantages in various aspects, for example, excellent mileage, no discharge of pollution materials, or reduction in discharge of pollution materials, and thus, people using the hybrid car or the electric vehicle have been increasing.
A secondary battery pack used in a hybrid car or an electric vehicle includes a plurality of secondary batteries, and the plurality of secondary batteries may be connected in series and/or in parallel with one another based on a required capacity and output. In addition, the secondary battery pack may further include a stacking frame for stacking the plurality of secondary batteries, a control device such as a BMS for controlling charging/discharging states of the secondary batteries, and a pack case configuring an outer appearance and protecting the above elements against outside.
In addition, an electrode terminal of the secondary battery pack may be electrically connected to a car driving motor via a high voltage cable, and generally the electrode terminal is exposed to an outer part of the pack case after passing through a terminal installation through hole provided in the pack case.
The pack case is required to have impact resistance, to block infiltration of impurities, and to have a predetermined level of water-resistant performance, and a space between the electrode terminal and the terminal installation through hole has to be sealed. To do this, secondary battery packs according to the related art generally use a gasket of a rubber material or an O-ring to seal between the electrode terminal and the terminal installation through hole.
However, according to the sealing structure using the O-ring as above, the O-ring may become limp when an internal pressure and an internal temperature in the secondary battery pack increase, and accordingly a leakage may occur around the terminal installation through hole. Also, the O-ring may not be completely adhered to an internal surface of the terminal installation through hole due to a dimensional error of the terminal installation through hole or an assembling error with respect to the electrode terminal during manufacturing the pack case. In this case, a sealing property between the terminal installation through hole of the pack case and the electrode terminal greatly degrades.